3 files changed, 47 insertions, 0 deletions

diff --git a/crates/ide_db/src/helpers.rs b/crates/ide_db/src/helpers.rs
index 66798ea3a..720de0d1f 100644
--- a/crates/ide_db/src/helpers.rs
+++ b/crates/ide_db/src/helpers.rs
@@ -1,6 +1,7 @@
 //! A module with ide helpers for high-level ide features.
 pub mod insert_use;
 pub mod import_assets;
+pub mod rust_doc;
 
 use std::collections::VecDeque;
 
@@ -113,6 +114,10 @@ impl FamousDefs<'_, '_> {
         self.find_module("core:iter")
     }
 
+    pub fn core_ops_Deref(&self) -> Option<Trait> {
+        self.find_trait("core:ops:Deref")
+    }
+
     fn find_trait(&self, path: &str) -> Option<Trait> {
         match self.find_def(path)? {
             hir::ScopeDef::ModuleDef(hir::ModuleDef::Trait(it)) => Some(it),
diff --git a/crates/ide_db/src/helpers/famous_defs_fixture.rs b/crates/ide_db/src/helpers/famous_defs_fixture.rs
index 4d79e064e..29ae12dcf 100644
--- a/crates/ide_db/src/helpers/famous_defs_fixture.rs
+++ b/crates/ide_db/src/helpers/famous_defs_fixture.rs
@@ -112,6 +112,12 @@ pub mod ops {
         type Output;
         extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
     }
+
+    #[lang = "deref"]
+    pub trait Deref {
+        type Target: ?Sized;
+        fn deref(&self) -> &Self::Target;
+    }
 }
 
 pub mod option {
@@ -141,3 +147,5 @@ mod return_keyword {}
 
 /// Docs for prim_str
 mod prim_str {}
+
+pub use core::ops;
\ No newline at end of file
diff --git a/crates/ide_db/src/helpers/rust_doc.rs b/crates/ide_db/src/helpers/rust_doc.rs
new file mode 100644
index 000000000..e27e23867
--- /dev/null
+++ b/crates/ide_db/src/helpers/rust_doc.rs
@@ -0,0 +1,34 @@
+//! Rustdoc specific doc comment handling
+
+// stripped down version of https://github.com/rust-lang/rust/blob/392ba2ba1a7d6c542d2459fb8133bebf62a4a423/src/librustdoc/html/markdown.rs#L810-L933
+pub fn is_rust_fence(s: &str) -> bool {
+    let mut seen_rust_tags = false;
+    let mut seen_other_tags = false;
+
+    let tokens = s
+        .trim()
+        .split(|c| c == ',' || c == ' ' || c == '\t')
+        .map(str::trim)
+        .filter(|t| !t.is_empty());
+
+    for token in tokens {
+        match token {
+            "should_panic" | "no_run" | "ignore" | "allow_fail" => {
+                seen_rust_tags = !seen_other_tags
+            }
+            "rust" => seen_rust_tags = true,
+            "test_harness" | "compile_fail" => seen_rust_tags = !seen_other_tags || seen_rust_tags,
+            x if x.starts_with("edition") => {}
+            x if x.starts_with('E') && x.len() == 5 => {
+                if x[1..].parse::<u32>().is_ok() {
+                    seen_rust_tags = !seen_other_tags || seen_rust_tags;
+                } else {
+                    seen_other_tags = true;
+                }
+            }
+            _ => seen_other_tags = true,
+        }
+    }
+
+    !seen_other_tags || seen_rust_tags
+}